<!-- 封装好分页器 -->
<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-if="startNumendNum.start > 1"
      @click="$emit('getPageNo', 1)"
      :class="{ active: pageNo == 1 }"
    >
      1
    </button>
    <button v-if="startNumendNum.start > 2">....</button>

    <!-- 页码器中间部分 -->
    <button
      v-for="(page, index) in startNumendNum.end"
      :key="index"
      v-show="page >= startNumendNum.start"
      @click="$emit('getPageNo', page)"
      :class="{ active: pageNo == page }"
    >
      {{ page }}
    </button>

    <button v-if="startNumendNum.end < totlePage - 1">....</button>
    <button
      v-if="startNumendNum.end < totlePage"
      @click="$emit('getPageNo', totlePage)"
      :class="{ active: pageNo == totlePage }"
    >
      {{ totlePage }}
    </button>
    <button
      :disabled="pageNo == totlePage"
      @click="$emit('getPageNo', pageNo + 1)"
    >
      下一页
    </button>

    <button style="margin-left: 30px">共{{ totle }}条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["pageNo", "pageSize", "totle", "continues"],
  computed: {
    //总共多少页
    totlePage () {
      //向上取值
      return Math.ceil(this.totle / this.pageSize)
    },
    startNumendNum () {
      const { continues, pageNo, totlePage } = this
      //先定义两个变量存储起始数据和结束数据
      let start = 0, end = 0
      //连续页码数字是5【至少是5页】，如果出现不正常的现象【就是不够5页】
      //不正常现象【总页数没有连续页码多】
      if (continues > totlePage) {
        start = 1
        end = totlePage
      }
      else {
        //正常现象【连续页码5，总页数一定大于5】
        start = pageNo - (continues - 1) / 2
        end = pageNo + (continues - 1) / 2
        // 当数据出现不正常的现象【start数字出现0或负数时】
        if (start < 1) {
          start = 1
          end = continues
        }
        // 当数据出现不正常的现象【end数字出现大于总页码数】
        if (end > totlePage) {
          start = totlePage - continues + 1
          end = totlePage
        }
      }
      return { start, end }
    }
  }
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active {
  background: skyblue;
}
</style>